OpenQASM

OpenQASM is an imperative programming language for describing quantum circuits. It is capable of
describing universal quantum computing using the circuit model, measurement-based model,
and near-term quantum computing experiments.

This repo contains the OpenQASM specification, examples, and tools for the OpenQASM intermediate representation.

OpenQASM started as a Qiskit project

Call for Applicants for TSC Secretary!

We are searching for candidates for the role of TSC Secretary.
The TSC will select a new Secretary during a TSC meeting in April, 2025.
Candidates should familiarize themselves with the responsibilties of the role.
If you are interested in presenting yourself as a candidate, please contact Jack Woehr,
the current Secretary, at jack.woehr@procern.com before April, 2025.

Current version: 3.1

• Live language specification version 3.1

• The branch of this repository for the previous version: OpenQASM 2.0

About this project

In this repository, you’ll find all the documentation related to OpenQASM, some useful OpenQASM examples, and a reference grammar.

Language specs

The live language documentation specification.

Examples

An example of OpenQASM 3.0 source code is given below. Several more examples may be found in the examples folder.

/*
 * Repeat-until-success circuit for Rz(theta),
 * cos(theta-pi)=3/5, from Nielsen and Chuang, Chapter 4.
 */
OPENQASM 3;
include "stdgates.inc";
/*
 * Applies identity if out is 01, 10, or 11 and a Z-rotation by
 * theta + pi where cos(theta)=3/5 if out is 00.
 * The 00 outcome occurs with probability 5/8.
 */
def segment qubit[2] anc, qubit psi -> bit[2] {
  bit[2] b;
  reset anc;
  h anc;
  ccx anc[0], anc[1], psi;
  s psi;
  ccx anc[0], anc[1], psi;
  z psi;
  h anc;
  measure anc -> b;
  return b;
}
qubit input;
qubit[2] ancilla;
bit[2] flags = "11";
bit output;
reset input;
h input;
// braces are optional in this case
while(int(flags) != 0) {
  flags = segment ancilla, input;
}
rz(pi - arccos(3 / 5)) input;
h input;
output = measure input;  // should get zero

Citation format

For research papers, we encourage authors to reference.

• [Version 3.0] Andrew W. Cross, Ali Javadi-Abhari, Thomas Alexander, Niel de Beaudrap, Lev S. Bishop, Steven Heidel, Colm A. Ryan, John Smolin, Jay M. Gambetta, Blake R. Johnson “OpenQASM 3: A broader and deeper quantum assembly language” [arxiv:2104.14722].
• [Previous Version: 2.0] Andrew W. Cross, Lev S. Bishop, John A. Smolin, Jay M. Gambetta “Open Quantum Assembly Language” [arXiv:1707.03429].

Governance

The OpenQASM project has a process for accepting changes to the language and making decisions codified in its governance model.

License

This project is licensed under the Apache License 2.0 - see the LICENSE file for details.

Contributing

If you’d like to help please take a look to our contribution guidelines. This project adheres to a Code of Conduct. By participating, you are expected to uphold this code.

Release Notes

See the section on Release Notes contribution guidelines.